Hypertension, or high blood pressure, is a chronic condition which is generally asymptomatic but is a risk factor for a variety of medically significant outcomes, including stroke, heart failure, and coronary artery disease. It has a large impact on public health and healthcare spending, affecting between 16 and 37% of the world population. Treatment of high blood pressure is readily available via lifestyle changes and medication, but in order to determine who needs such treatment, accurate measurement of blood pressure is a necessity. Even after the initial diagnosis, monitoring blood pressure is helpful for managing hypertension, as doctors can monitor whether patients are keeping their pressure within recommended limits.
Measuring blood pressure (BP) involves determining a systolic (SBP) and diastolic (DBP) value; representing the peak and minimum values of blood pressure in the artery, respectively. The clinical standard of attaining these measurements involves a stethoscope and a sphygmomanometer (inflatable cuff with pressure gauge) and listening for the changes in blood flow as the artery is completely occluded, partially occluded, and unoccluded; this is known as the auscultatory method. Patients will often monitor blood pressure at home with an automated device, also with an inflatable cuff, which uses the oscillometric method of measurement, an approach with a similar principle that attempts to determine the changes in the pressure wave electronically (with some loss in accuracy). These single-point measurements, however, do not necessarily predict whether a patient is truly hypertensive. Blood pressure varies throughout the day, and a patient's blood pressure is often higher at the doctor's office at midday versus when relaxing at home, due both to the physical activity associated with travel to the clinic and the patient's anxiety from meeting with the doctor (known as the “white coat effect”).
An increasing body of evidence suggests that ambulatory BP monitoring (ABPM) provides a much more complete measure of blood pressure than either a single measurement at the clinician's office or a single measurement with a home blood pressure device, and as such provides significant value in the diagnosis and treatment of hypertension. The current standard in ABPM is an inflatable oscillometric cuff (typically with a tube going to a base module) that must be worn at all times; the cuff will inflate periodically and at least partially immobilize the wearer's arm. As a result, ABPM studies are logistically difficult; periodic inflation is at best uncomfortable, at worst painful, and often disrupts sleep during overnight studies. This has hindered the adoption of ABPM in practice.